src/module/traits/Trait.js

/**
 * Provides a wrapper around a data field which may be an array, function or other primitive value.
 */
export default class Trait
{
   /**
    * Initializes trait data.
    *
    * @param {string}   metric - The name of Halstead metric being stored.
    * @param {*}        data - Data to wrap.
    */
   constructor(metric, data)
   {
      /* istanbul ignore if */
      if (typeof metric !== 'string') { throw new TypeError('ctor error: metric is not a `string`.'); }

      /**
       * Stores the data to wrap.
       * @type {*}
       * @private
       */
      this._data = data;

      /**
       * Stores the Trait metric type.
       * @type {string}
       * @private
       */
      this._metric = metric;
   }

   /**
    * Returns the associated metric type.
    *
    * @returns {string}
    */
   get metric() { return this._metric; }

   /**
    * Returns the typeof data being wrapped.
    *
    * @returns {string}
    */
   get type() { return typeof this._data; }

   /**
    * Returns the value of the given data. If the wrapped data is a function it is invoked with the given `params`
    * otherwise the data is returned directly. If the wrapped data is an array a mapped version is returned
    * with each entry that is a function being invoked with the given `params`.
    *
    * @param {*}  params - Provides parameters which are forwarded onto any data stored as a function. Normally
    *                      `params` should be the `current AST node, parent AST node, ... optional data`.
    *
    * @returns {*}
    */
   valueOf(...params)
   {
      if (Array.isArray(this._data))
      {
         return this._data.map((entry) => typeof entry === 'function' ? entry(...params) : entry);
      }

      return typeof this._data === 'function' ? this._data(...params) : this._data;
   }
}